Systems and Methods for Guidance and Placement of an Intravascular Device

ABSTRACT

A guidance and placement system and associated methods for assisting a clinician in the placement of a catheter or other medical device within the vasculature of a patient is disclosed. In one embodiment, a method for guiding a medical device to a desired location within a vasculature of a patient is also disclosed and comprises detecting an intravascular ECG signal of the patient and identifying a P-wave of a waveform of the intravascular ECG signal, wherein the P-wave varies according to proximity of the medical device to the desired location. The method further comprises determining whether the identified P-wave is elevated, determining a deflection value of the identified P-wave when the identified P-wave is elevated, and reporting information relating to a location of the medical device within the patient&#39;s vasculature at least partially according to the determined deflection value of the elevated P-wave.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/936,825, filed Feb. 6, 2014, and titled “SYSTEMS ANDMETHODS FOR GUIDANCE AND PLACEMENT OF AN INTRAVASCULAR DEVICE,” which isincorporated herein by reference in its entirety.

BRIEF SUMMARY

Briefly summarized, embodiments of the present invention are directed toa guidance and placement system for assisting a clinician in theplacement of a catheter or other medical device within the vasculatureof a patient, and related methods. The guidance and placement systemenables a distal tip of a catheter to be placed within the patientvasculature in desired proximity to the patient's heart using ECGsignals produced by the heart.

In one embodiment, a method for guiding a medical device to a desiredlocation within a vasculature of a patient is disclosed. The methodcomprises detecting an intravascular ECG signal of the patient andidentifying a P-wave of a waveform of the intravascular ECG signal,wherein the P-wave varies according to proximity of the medical deviceto the desired location.

The method further comprises determining whether the identified P-waveis elevated, determining a deflection value of the identified P-wavewhen the identified P-wave is elevated, and reporting informationrelating to a location of the medical device within the patient'svasculature at least partially according to the determined deflectionvalue of the elevated P-wave.

In one embodiment, the intended destination of the catheter within thepatient body is such that the distal tip of the catheter is disposed inthe lower ⅓^(rd) portion of the superior vena cava (“SVC”). The guidanceand placement system analyzes the ECG signals of the patient todetermine when the catheter has reached its intended destination withinthe vasculature, then notifies the clinician via a display, forinstance. Thus, the system includes an ECG modality for assisting inmedical device placement within the patient.

These and other features of embodiments of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of embodiments of theinvention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the present disclosure will be renderedby reference to specific embodiments thereof that are illustrated in theappended drawings. It is appreciated that these drawings depict onlytypical embodiments of the invention and are therefore not to beconsidered limiting of its scope. Example embodiments of the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a block diagram showing various components of a guidance andplacement system according to one embodiment;

FIG. 2 shows the system of FIG. 1 in use to guide insertion andplacement of a catheter into a body of a patient;

FIG. 3 shows various details of an ECG complex;

FIG. 4 shows various details of an ECG trace;

FIG. 5 is a block diagram showing various aspects of a guidance andplacement system according to one embodiment;

FIG. 6 is a block diagram showing various stages of a method for guidinga medical device according to one embodiment;

FIG. 7 shows various details of a captured intravascular ECG complexaccording to one embodiment;

FIG. 8 shows various details of a captured intravascular ECG complexaccording to one embodiment;

FIG. 9 shows a decision tree for determining display output to aguidance and placement system according to one embodiment;

FIGS. 10A-10C show various screenshots of a display of a guidance andplacement system according to one embodiment;

FIG. 11 is a block diagram showing various stages of a method forguiding a medical device according to one embodiment;

FIG. 12 is a simplified view of a heart with possible reporting zonessuperimposed thereon, according to one embodiment; and

FIG. 13 shows a decision tree for determining display output to aguidance and placement system according to one embodiment.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

Reference will now be made to figures wherein like structures will beprovided with like reference designations. It is understood that thedrawings are diagrammatic and schematic representations of exemplaryembodiments of the present invention, and are neither limiting nornecessarily drawn to scale.

For clarity it is to be understood that the word “proximal” refers to adirection relatively closer to a clinician using the device to bedescribed herein, while the word “distal” refers to a directionrelatively further from the clinician. For example, the end of acatheter placed within the body of a patient is considered a distal endof the catheter, while the catheter end remaining outside the body is aproximal end of the catheter. Also, the words “including,” “has,” and“having,” as used herein, including the claims, shall have the samemeaning as the word “comprising.”

Embodiments of the present invention are generally directed to aguidance and placement system, also referred to herein as a “placementsystem” or “system,” for assisting a clinician in the placement of acatheter or other medical device within the body of a patient, such aswithin the vasculature. In one embodiment, the guidance and placementsystem enables a distal tip of a catheter to be placed within thepatient vasculature in desired proximity to the heart using ECG signalsproduced by the patient's heart. In one embodiment, the medical deviceincludes a catheter and the intended destination of the catheter withinthe patient body is such that the distal tip of the catheter is disposedin the lower ⅓^(rd) portion of the superior vena cava (“SVC”). Theguidance and placement system analyzes the ECG signals of the patient todetermine when the catheter has reached its intended destination withinthe vasculature, then notifies the clinician via a display, forinstance. Thus, the system includes an ECG modality for assisting inmedical device placement within the patient.

In one embodiment, the above-referenced ECG guidance modality of theguidance and placement system is accompanied by an ultrasound (“US”)modality to assist with initial insertion of the medical device into thebody, and a magnetic element-based tracking, or tip location system(“TLS”) modality to track the position and orientation of the medicaldevice as it advances toward its intended destination.

Reference is first made to FIGS. 1 and 2 which depict various componentsof a placement system (“system”), generally designated at 10, configuredin accordance with one example embodiment of the present invention. Asshown, the system 10 generally includes a console 20, display 30, probe40, and sensor 50, each of which is described in further detail below.

FIG. 2 shows the general relation of these components to a patient 70during a procedure to place a catheter 72 into the patient vasculaturethrough a skin insertion site 73. FIG. 2 shows that the catheter 72generally includes a proximal portion 74 that remains exterior to thepatient and a distal potion 76 that resides within the patientvasculature after placement is complete. In the present embodiment, thesystem 10 is employed to ultimately position a distal tip 76A of thecatheter 72 in a desired position within the patient vasculature. In oneembodiment, the desired position for the catheter distal tip 76A isproximate the patient's heart, such as in the lower one-third (⅓^(rd))portion of the Superior Vena Cava (“SVC”). Of course, the system 10 canbe employed to place the catheter distal tip in other locations. Thecatheter proximal portion 74 further includes a hub 74A that providesfluid communication between the one or more lumens of the catheter 72and one or more extension legs 74B extending proximally from the hub.

A processor 22, including non-volatile memory such as EEPROM forinstance, is included in the console 20 for controlling system functionduring operation of the system 10, thus acting as a control processor. Adigital controller/analog interface 24 is also included with the console20 and is in communication with both the processor 22 and other systemcomponents to govern interfacing between the probe 40, sensor 50, andother system components.

The system 10 further includes ports 52 for connection with the sensor50 and optional components 54 including a printer, storage media,keyboard, etc. The ports in one embodiment are USB ports, though otherport types or a combination of port types can be used for this and theother interfaces connections described herein. A power connection 56 isincluded with the console 20 to enable operable connection to anexternal power supply 58. An internal battery 60 can also be employed,either with or exclusive of an external power supply. Power managementcircuitry 59 is included with the digital controller/analog interface 24of the console to regulate power use and distribution.

The display 30 in the present embodiment is integrated into the console20 and is used to display information to the clinician during thecatheter placement procedure. In another embodiment, the display may beseparate from the console. As will be seen, the content depicted by thedisplay 30 changes according to which mode the catheter placement systemis in: US, TLS, or in other embodiments, ECG tip confirmation. In oneembodiment, a console button interface 32 and buttons included on theprobe 40 can be used to immediately call up a desired mode to thedisplay 30 by the clinician to assist in the placement procedure. In oneembodiment, information from multiple modes, such as TLS and ECG, may bedisplayed simultaneously. Thus, the single display 30 of the systemconsole 20 can be employed for ultrasound guidance in accessing apatient's vasculature, TLS guidance during catheter advancement throughthe vasculature, and (as in later embodiments) ECG-based confirmation ofcatheter distal tip placement with respect to a node of the patient'sheart. In one embodiment, the display 30 is an LCD device.

The probe 40 is employed in connection with the first modality mentionedabove, i.e., ultrasound (“US”)-based visualization of a vessel, such asa vein, in preparation for insertion of the catheter 72 into thevasculature. Such visualization gives real time ultrasound guidance forintroducing the catheter into the vasculature of the patient and assistsin reducing complications typically associated with such introduction,including inadvertent arterial puncture, hematoma, pneumothorax, etc.

As such, in one embodiment a clinician employs the first, US, modalityto determine a suitable insertion site and establish vascular access,such as with a needle and introducer, then with the catheter. Theclinician can then seamlessly switch, via button pushes on the probebutton pad, to the second, TLS, modality without having to reach out ofthe sterile field. The TLS mode can then be used to assist inadvancement of the catheter 72 through the vasculature toward anintended destination.

FIG. 1 shows that the probe 40 further includes button and memorycontroller 42 for governing button and probe operation. The button andmemory controller 42 can include non-volatile memory, such as EEPROM, inone embodiment. The button and memory controller 42 is in operablecommunication with a probe interface 44 of the console 20, whichincludes a piezo input/output component 44A for interfacing with theprobe piezoelectric array and a button and memory input/output component44B for interfacing with the button and memory controller 42.

Note that while a vein is typically depicted on the display 30 duringuse of the system 10 in the US modality, other body lumens or portionscan be imaged in other embodiments. Note that the US mode can besimultaneously depicted on the display 30 with other modes, such as theTLS mode or ECG mode, if desired. In addition to the visual display 30,aural information, such as beeps, tones, etc., or vibratory/motion-basedcues can also be employed by the system 10 to assist the clinicianduring catheter placement. Moreover, the buttons included on the probe40 and the console button interface 32 can be configured in a variety ofways, including the use of user input controls in addition to buttons,such as slide switches, toggle switches, electronic or touch-sensitivepads, etc. Additionally, US, TLS, and ECG activities can occursimultaneously or exclusively during use of the system 10.

As just described, the handheld ultrasound probe 40 is employed as partof the integrated catheter placement system 10 to enable USvisualization of the peripheral vasculature of a patient in preparationfor transcutaneous introduction of the catheter. In the present exampleembodiment, however, the probe is also employed to control functionalityof the TLS portion, or second modality, of the system 10 when navigatingthe catheter toward its desired destination within the vasculature asdescribed below. Again, as the probe 40 is used within the sterile fieldof the patient, this feature enables TLS functionality to be controlledentirely from within the sterile field. Thus the probe 40 is adual-purpose device, enabling convenient control of both US and TLSfunctionality of the system 10 from the sterile field. In oneembodiment, the probe can also be employed to control some or allECG-related functionality, or third modality, of the catheter placementsystem 10, as described further below.

The catheter placement system 10 further includes the second modalitymentioned above, i.e., the magnetically-based catheter TLS, or tiplocation system. The TLS enables the clinician to quickly locate andconfirm the position and/or orientation of the catheter 72, such as aperipherally-inserted central catheter (“PICC”), central venous catheter(“CVC”), or other suitable catheter or medical device, during initialplacement into and advancement through the vasculature of the patient70. Specifically, the TLS modality detects a magnetic field generated bya magnetic element-equipped tip location stylet, which is pre-loaded inone embodiment into a longitudinally defined lumen of the catheter 72,thus enabling the clinician to ascertain the general location andorientation of the catheter tip within the patient body. In oneembodiment, the magnetic assembly can be tracked using the teachings ofone or more of the following U.S. Pat. Nos. 5,775,322; 5,879,297;6,129,668; 6,216,028; and 6,263,230. The contents of the afore-mentionedU.S. patents are incorporated herein by reference in their entireties.The TLS also displays the direction in which the catheter tip ispointing, thus further assisting accurate catheter placement. The TLSfurther assists the clinician in determining when a malposition of thecatheter tip has occurred, such as in the case where the tip hasdeviated from a desired venous path into another vein.

As mentioned, the TLS utilizes a stylet to enable the distal end of thecatheter 72 to be tracked during its advancement through thevasculature. In one embodiment, the stylet includes a proximal end and adistal end, with a handle included at the proximal end and a core wireextending distally therefrom. A magnetic assembly is disposed distallyof the core wire. The magnetic assembly includes one or more magneticelements disposed adjacent one another proximate the stylet distal endand encapsulated by tubing. In the present embodiment, a plurality ofmagnetic elements is included, each element including a solid,cylindrically shaped ferromagnetic stacked end-to-end with the othermagnetic elements. An adhesive tip can fill the distal tip of thetubing, distally to the magnetic elements.

Note that in other embodiments, the magnetic elements may vary from thedesign in not only shape, but also composition, number, size, magnetictype, and position in the stylet distal segment. For example, in oneembodiment, the plurality of ferromagnetic magnetic elements is replacedwith an electromagnetic assembly, such as an electromagnetic coil, whichproduces a magnetic field for detection by the sensor. Another exampleof an assembly usable here can be found in U.S. Pat. No. 5,099,845,entitled “Medical Instrument Location Means,” which is incorporatedherein by reference in its entirety. Yet other examples of styletsincluding magnetic elements that can be employed with the TLS modalitycan be found in U.S. Pat. No. 8,784,336, entitled “Stylet Apparatusesand Methods of Manufacture,” which is incorporated herein by referencein its entirety. These and other variations are therefore contemplatedby embodiments of the present invention. It should appreciated hereinthat “stylet” as used herein can include any one of a variety of devicesconfigured for removable placement within a lumen of the catheter toassist in placing a distal end of the catheter in a desired locationwithin the patient's vasculature. In one embodiment, the stylet includesa guidewire.

FIG. 2 shows disposal of a stylet 130 substantially within a lumen inthe catheter 72 such that the proximal portion thereof extendsproximally from the catheter lumen, through the hub 74A and out througha selected one of the extension legs 74B. So disposed within a lumen ofthe catheter, the distal end 100B of the stylet 100 in the presentembodiment is substantially co-terminal with the distal catheter end 76Asuch that detection by the TLS of the stylet distal end correspondinglyindicates the location of the catheter distal end. In other embodiments,other positional relationships between the distal ends of the stylet andcatheter or medical device are possible.

The TLS sensor 50 is employed by the system 10 during TLS operation todetect the magnetic field produced by the magnetic elements of thestylet 130. As seen in FIG. 2, the TLS sensor 50 is placed on the chestof the patient during catheter insertion. The TLS sensor 50 ispositioned on the chest of the patient in a predetermined location, suchas through the use of external body landmarks, to enable the magneticfield of the stylet magnetic elements, disposed in the catheter 72 asdescribed above, to be detected during catheter transit through thepatient vasculature. Again, as the magnetic elements of the styletmagnetic assembly are co-terminal with the distal end 76A of thecatheter 72 in one embodiment (FIG. 2), detection by the TLS sensor 50of the magnetic field of the magnetic elements provides information tothe clinician as to the position and orientation of the catheter distalend during its transit.

In greater detail, the TLS sensor 50 is operably connected to theconsole 20 of the system 10 via one or more of the ports 52, as shown inFIG. 1. Note that other connection schemes between the TLS sensor andthe system console can also be used without limitation. As justdescribed, the magnetic elements are employed in the stylet 130 toenable the position of the catheter distal end 76A (FIG. 2) to beobservable relative to the TLS sensor 50 placed on the patient's chest.Detection by the TLS sensor 50 of the stylet magnetic elements isgraphically displayed on the display 30 of the console 20 during TLSmode. In this way, a clinician placing the catheter is able to generallydetermine the location of the catheter distal end 76A within the patientvasculature relative o the TLS sensor 50 and detect when cathetermalposition, such as advancement of the catheter along an undesiredvein, is occurring.

As discussed above, the system 10 includes additional functionality inthe present embodiment wherein determination of the proximity of thecatheter distal tip 76A relative to a sino-atrial (“SA”) or otherelectrical impulse-emitting node of the heart of the patient 70 can bedetermined, thus providing enhanced ability to accurately place thecatheter distal tip in a desired location proximate the node. Alsoreferred to herein as “ECG” or “ECG-based tip confirmation,” this thirdmodality of the system 10 enables detection of ECG signals from the SAnode in order to place the catheter distal tip in a desired locationwithin the patient vasculature. Note that the US, TLS, and ECGmodalities are seamlessly combined in the present system 10, but can beemployed in concert or individually to assist in catheter placement. Inone embodiment, it is understood that the ECG modality as describedherein can be included in a stand-alone system without the inclusion ofthe US and TLS modalities. Thus, the environments in which theembodiments herein are described are understood as merely exampleenvironments and are not considered limiting of the present disclosure.

As described, the catheter stylet 130 is removably predisposed withinthe lumen of the catheter 72 being inserted into the patient 70 via theinsertion site 73. The stylet 130, in addition to including a magneticassembly for the magnetically-based TLS modality, includes a sensingcomponent, i.e., an internal, intravascular ECG sensor assembly,proximate its distal end and including a portion that is co-terminalwith the distal end of the catheter tip for intravascularly sensing ECGsignals produced by the SA node, in the present embodiment when thecatheter 72 and accompanying stylet 130 are disposed within the patientvasculature. The intravascular ECG sensor assembly is also referred toherein as an internal or intravascular ECG sensor component.

The stylet 130 includes a tether 134 extending from its proximal endthat operably connects to the TLS sensor 50, though other connectionschemes to the system 10 are contemplated. As will be described infurther detail, the stylet tether 134 permits ECG signals detected bythe ECG sensor assembly included on a distal portion of the stylet 130to be conveyed to the TLS sensor 50 during confirmation of the cathetertip location as part of the ECG signal-based tip confirmation modality.

External reference and ground ECG electrodes 136 attach to the body ofthe patient 70 in the present embodiment and are operably attached tothe TLS sensor 50 to provide an external baseline ECG signal to thesystem 10 and to enable the system to filter out high level electricalactivity unrelated to the electrical activity of the SA node of theheart, thus enabling the ECG-based tip confirmation functionality. Asshown, in the present embodiment, one external electrode 136 is placedon the patient skin proximate the upper right shoulder (“right arm”placement) while another external electrode is placed proximate thelower left abdomen (“left leg” placement). This electrode arrangementprovides a lead II configuration according to Einthoven's triangle ofelectrocardiography. Operable attachment of the external electrodes 136with the sensor 50 enables the ECG signals detected by the externalelectrodes to be conveyed to the console 20 of the system 10 or toanother suitable destination. As such, the external electrodes 136 serveas one example of an external ECG sensor component. Other externalsensors for detecting a baseline ECG signal external to the patient bodycan also be employed in other embodiments. In addition, other electrodelocations are also possible.

Together with the external ECG signal received from the external ECGsensor component (i.e., the external ECG electrodes 136 placed on thepatient's skin), an internal, intravascular ECG signal sensed by theinternal ECG sensor component (i.e., the stylet ECG sensor assembly ofthe stylet 130), is received by the TLS sensor 50 positioned on thepatient's chest (FIG. 10) or other designated component of the system10. The TLS sensor 50 and/or console processor 22 can process theexternal and internal ECG signal data to produce one or moreelectrocardiogram traces, including a series of discrete ECG complexes,on the display 30, as will be described. In the case where the TLSsensor 50 processes the external and internal ECG signal data, aprocessor is included therein to perform the intended functionality. Ifthe console 20 processes the ECG signal data, the processor 22,controller 24, or other processor can be utilized in the console toprocess the data.

Thus, as it is advanced through the patient vasculature, the catheter 72equipped with the stylet 130 as described above can advance under theTLS sensor 50, which is positioned on the chest of the patient as shownin FIG. 10. This enables the TLS sensor 50 to detect the position of themagnetic assembly of the stylet 130 (described further above), which issubstantially co-terminal with the distal tip 76A of the catheter aslocated within the patient's vasculature. The detection by the TLSsensor 50 of the stylet magnetic assembly is depicted on the display 30during ECG mode.

The display 30 can further depict during ECG mode one or more ECGelectrocardiogram traces produced as a result of patient heart'selectrical activity as detected by the external and internal ECG sensorcomponents described above. In greater detail, the ECG electricalactivity of the SA node, including the P-wave of the trace, is detectedby the external and internal sensor components and forwarded to the TLSsensor 50 and console 20. The ECG electrical activity is then processedfor depiction on the display 30, as will be described further below.

A clinician placing the catheter can then observe the ECG data, whichassists in determining optimum placement of the distal tip 76A of thecatheter 72, such as proximate the SA node, for instance. In oneembodiment, the console 20 includes the electronic components, such asthe processor 22 (FIG. 1), necessary to receive and process the signalsdetected by the external and internal sensor components. In anotherembodiment, the TLS sensor 50 can include the necessary electroniccomponents processing the ECG signals.

As already discussed, the display 30 is used to display information tothe clinician during the catheter placement procedure. The content ofthe display 30 changes according to which mode the catheter placementsystem is in: US, TLS, or ECG. Any of the three modes can be immediatelycalled up to the display 30 by the clinician, and in some casesinformation from multiple modes, such as TLS and ECG, may be displayedsimultaneously. In one embodiment, as before, the mode the system is inmay be controlled by the control buttons included on the handheld probe40, thus eliminating the need for the clinician to reach out of thesterile field (such as touching the button interface 32 of the console20) to change modes. Thus, in the present embodiment the probe 40 isemployed to also control some or all ECG-related functionality of thesystem 10. Note that the button interface 32 or other inputconfigurations can also be used to control system functionality. Also,in addition to the visual display 30, aural information, such as beeps,tones, etc., can also be employed by the system to assist the clinicianduring catheter placement.

Note that further details regarding the system 10 can be found in U.S.Pat. No. 8,848,382, issued Sep. 30, 2014, and entitled “Apparatus andDisplay Methods Relating to Intravascular Placement of a Catheter,”which is incorporated herein by reference in its entirety.

FIG. 3 depicts various details of an ECG complex 1176 of anelectrocardiogram trace of a patient, including an isoelectric line1176A, a P-wave 1176P, a Q-wave 1176Q, an R-wave 1176R, and S-wave1176S, and a T-wave 1176T. FIG. 4 depicts further details andrelationships between adjacent ECG complexes 1176, including an RRinterval 1180 between successive ECG complexes, which is typicallyemployed to determine the heart rate of the patient. These waves andintervals are used by the system 10 in the present embodiment todetermine proximity of the catheter 72 or other medical device to the SAnode or other desired location within the patient vasculature, asdescribed herein.

FIG. 5 depicts an overview of the system 10 and a method 1200 forguiding the catheter to a desired intravascular location. As shown, themethod 1200 employs external ECG data 1210 acquired from the externalelectrodes 136 (also referred to herein as external ECG sensorcomponents) placed externally on the skin of the patient 70, as shown inFIG. 2, though the particular location of the electrodes can vary. Asmentioned, the external electrodes 136 in the present embodiment areplaced in a right arm/left leg “Lead II” arrangement.

The method 1200 further employs internal, intravascular ECG data 1212acquired from the above-described internal ECG sensor component,implemented in the present embodiment as the ECG sensor assembly of thestylet 130. The external and intravascular ECG data 1210, 1212 isreceived and conditioned by processing componentry located in the TLSsensor 50 (FIG. 2) in one embodiment, though other system components canalso include this functionality, such as the processor 22 of the systemconsole 20.

Briefly and in accordance with one embodiment, the external andintravascular ECG data 1210, 1212 are input into a P-wave algorithm 1216in order to determine intravascular proximity of the stylet distal tipto the SA node or other desired location within the patient 70 (FIG. 2).The P-wave algorithm 1216 in one embodiment is executed by a processorincluded in the TLS sensor 50, or in another embodiment by the processor22 of the console 20, or by another suitable processor.

Output produced by the P-wave algorithm 1216 includes data relating toanalysis of the P-wave of one or more ECG complexes of the intravascularECG signal and corresponding zone designations relating to the proximityof the distal tip of the stylet 130 of the catheter 72 to the SA node ofthe heart. The output is received (via arrow 1216A) to a systemapplication executed by the processor 22 of the system console 20, whichcan then output (via arrow 1218A) graphical information relating to thestylet distal tip position for depiction on a system display 1220, suchas the display 30 of the system 10 (FIGS. 1, 2). Observation of thedisplay 30 by the clinician of the information relating to theintravascular position of the stylet distal tip, which in the presentembodiment is co-terminal with the distal tip of the catheter 72, aidsthe clinician in placing the catheter distal tip in the desiredlocation.

FIG. 6 further depicts various details regarding the method 1200 (FIG.5) for guiding the catheter according to the present embodiment. Asshown, the method 1200 includes an external ECG process 1222 utilizingthe external ECG data 1210 and an intravascular ECG process 1224utilizing the intravascular ECG data 1212, with various intermediateactions. Again, in one embodiment the method 1200 is executed by asuitable processor, such as the processor 22 disposed in the systemconsole 22 or a processor disposed in the TLS sensor 50, utilizingexternal and intravascular ECG signal data detected by the systemcomponents, as described above.

The top portion of FIG. 6 shows that the external ECG signal data 1210,including ECG complexes of an external ECG signal detected by theexternal sensor component (i.e., the skin-placed external electrodes136), is received by the TLS sensor 50. Likewise, the intravascular ECGsignal data 1212, including ECG complexes of an intravascular ECG signaldetected by the intravascular sensor component (i.e., the stylet ECGsensor assembly of the stylet 70), is also received by the TLS sensor50. These data are utilized in the method 1200 as described below.

The external ECG process 1222, which utilizes the external ECG data1210, is performed first in the present embodiment. Note that theprocess 1222, as with the other processes to be described herein, can beperformed by a suitable processor included in the system 10 or operablyassociated therewith. As already mentioned, such a processor can includea processor of the TLS sensor 50, the processor 22 of the system console10, etc.

The external ECG process 1222 includes stage 1230 wherein a QRS complexof a current ECG complex, such as the ECG complex 1176 (FIG. 3), isidentified in the ECG signal of the external ECG signal data 1210. Inparticular, stage 1230 includes determining the location or point intime of occurrence of the QRS complex in the external ECG signal data1210, which is also referred to herein as time-stamping of the QRScomplex within the external ECG signal data 1210. Similar time-stampingcan occur for other identified aspects of the ECG complex(es) ofsucceeding stages. In one embodiment, a 16^(th)—order finite impulseresponse (“FIR”) filter is employed to identify two successive QRScomplexes (waveforms) in stage 1230. Other modes can also be employed toidentify this and other waveform components

Note that the external ECG signal data 1210 and the intravascular ECGsignal data 1212 are time-synchronous such that the occurrence of theQRS complex or other aspect of an ECG complex detected in the externalECG signal data 1210 will correspond in time with the same aspect of theECG complex detected in the intravascular ECG signal data 1212, in thepresent embodiment. Thus, the identified aspects of ECG complexes in theexternal ECG signal data 1210 can be used to find the correspondingaspects in the ECG complexes in the intravascular ECG signal data 1212.

At stage 1232, the time interval for the R-R interval, such as the R-Rinterval 1180 shown in FIG. 4, between two successive ECG complexes inthe external ECG signal data 1210 is determined. This can be used, amongother things, for determining patient heart rate.

At stage 1234, the T-wave, such as the T-wave 1176T of FIG. 3, isidentified from the current ECG complex of the external ECG signal data1210 under analysis. Finally, at stage 1236, the P-wave, such as theP-wave 1176P of FIG. 3, is identified from the current ECG complexes ofthe external ECG data 1210. With such identification, the time of onset(beginning), offset (ending), and maximum amplitude of the identifiedP-wave are performed at stage 1236 in the present embodiment.

Note that an algorithm to perform one embodiment of stages 1230 to 1236has been developed as a object library or software library from MoneboTechnologies, Inc., 1800 Barton Creek Blvd., Austin, Tex. 78735. In oneembodiment, the software library can be accessed via an applicationprogram interface (“API”) as a callable function. The software librarycan be accessed by the system application 1218 (FIG. 5). Note also that,in one embodiment, multiple ECG complexes of the external ECG signaldata 1210 can be analyzed in performing the above-described stages ofthe external ECG process 1222.

At stage 1240, a decision is made to confirm that the P-wave has beenidentified in stage 1236. If not, the method 1200 proceeds to stage1242, wherein data regarding the QRS location identified at stage 1230is passed to a new procedure at stage 1244. Indeed, at stage 1244, theP-wave is again identified, but it is identified in the intravascularECG signal data 1212, using the time-stamped location of the identifiedQRS complex of the external ECG signal data 1210 from stage 1230. Againnote that, because both the external and intravascular ECG data 1210,1212 are measurements of the electrical activity of the SA node of thepatient's heart, they are time-synchronized despite being detected viadifferent apparatus (i.e., the external electrodes 136 for the externalECG signal data, and the stylet sensor assembly of the stylet 130 forthe intravascular ECG signal data). Thus, identification of the QRScomplex of an ECG complex from the external ECG signal data 1210 willcorrespond in time/location to a QRS complex or other component of thecorresponding ECG complex in the intravascular ECG signal data 1212.

At stage 1246 it is determined whether the intravascular P-wave(identified from the intravascular ECG signal data 1212) has beensuccessfully identified in stage 1244. If the answer is “no,” theprocess forwards a “no report” signal to the system 10 at stage 1248. Ifthe answer at stage 1246 is “yes” as to successful identification of theintravascular P-wave, the time-stamped location of the intravascularP-wave is forwarded at stage 1250 to the intravascular ECG process 1224.Alternatively, if the answer at stage 1240 is “yes” as to successfulidentification of the external P-wave, the stages 1242, 1244, and 1246are skipped, as seen in FIG. 6, and the time-stamped external P-wave(identified from the external ECG signal data 1210) is forwarded atstage 1250 to the intravascular ECG process 1224. In one embodiment,time-stamping data regarding various aspects of the P-wave areforwarded, including time of P-wave onset, P-wave peak (or maximumamplitude), and P-wave offset.

Upon receipt of the P-wave location (via identification thereof in theexternal ECG signal data 1210 at stage 1236 or in the intravascular ECGsignal data 1212 at stage 1244) from stage 1250, the intravascular ECGprocess 1224 begins at stage 1260 by performing a frequency analysis ofthe P-wave as detected by the internal ECG sensor. In the presentembodiment and as executed by the processor 22 (FIG. 1) or othersuitable processing component, stage 1260 includes analyzing the P-wavein the frequency domain to determine whether it meets or exceeds apredetermined threshold value. In one embodiment, the frequency of theP-wave can be thought of as the inclined slope of the P-wave in the timedomain.

At stage 1264, an amplitude analysis of the P-wave is also performed inthe time domain to determine whether it meets or exceeds a predeterminedthreshold value. In the present embodiment, the P-wave is determined tobe at a maximum when its possesses the following threshold values: anamplitude of between about 250 microvolts and about 1500 microvolts ator above about 20 Hz; and a frequency (inclined slope) range between:exceeding about 10 microvolts per millisecond when the P-wave amplitudeis at about 250 microvolts and exceeding 60 microvolts per millisecondwhen the P-wave amplitude is at about 1500 microvolts. Of course, otherranges and values can be used in other embodiments according toapplication, desired sensitivity, intended target location, etc.

At stage 1262 an analysis is performed to determine whether noise in theintravascular ECG signal data 1212 exceeds acceptable levels such thatreliable P-wave determination is impossible. In detail, the process 1224at stage 1262 reports a value related to the level of noise encountered.In the present embodiment, the threshold noise values include: themaximum level of high frequency (i.e., greater than about 20 Hz) noisepresent between the offset, or end, of the QRS complex of an ECG complexand onset, or beginning, of the P-wave of the successive ECG complex isless than about 35 microvolts, with a ratio of the maximum level of highfrequency noise to the maximum amplitude of the high frequency componentof the P-wave in the current ECG complex is less than about 50%. Othernoise values can be employed by the process 1224 in determiningacceptable noise threshold levels.

At stage 1266, it is determined whether an elevated, or maximum P-wavein the ECG complex, such as that seen at 1176P in the ECG complex 1176of FIG. 7, has been identified. This is done by determining whether theabove-discussed P-wave frequency, amplitude and noise threshold values(determined in stages 1260, 1264, and 1262, respectively) have each beenmet. If one or more have not been met, the process forwards a “noreport” signal to the system 10 at stage 1248.

If each of the above threshold values of stages 1260, 1262, and 1264 hasbeen met, stage 1266 reports a “yes” and stage 1268 is executed, whereina deflection analysis of the P-wave is performed. FIG. 8 shows a P-waveportion of the ECG complex 1176 as including a deflection portion 1278,or negative P-wave component that dips below the isoelectric line 1176Abefore rising to form the inflected portion 1276—the portion of theP-wave rising above the isoelectric line of the P-wave. Stage 1268analyzes the P-wave for such a deflection. In the present embodiment,stage 1268 is performed by dividing the amplitude of the deflectionportion 1278 of the P-wave by the inflected portion 1276 of the P-wave,which yields a deflection percentage. The value of the deflectionpercentage enables the system 10 to determine the proximity of theintravascular ECG sensor (implemented as the stylet ECG sensor assemblyof the stylet 130 at the stylet distal tip), and hence the catheterdistal tip, to the SA node.

In the present embodiment, a deflection value of about 0% indicates thatthere is substantially no deflection of the P-wave and that the styletdistal tip is at or near a lower ⅓^(rd) portion 1354 of a SVC 1352 neara heart 1350 of the patient vasculature, referred to by the process 1224as zone 1, shown in FIG. 12. A deflection value of greater than about 0%but less than or equal to about 10% indicates that the P-wave isminimally deflected and that the stylet distal tip has passed but isnear the lower ⅓^(rd) portion 1354 of the SVC 1352, referred to by theprocess 1224 as zone 2. A deflection value of greater than about 10%indicates that the P-wave is significantly deflected and that the styletdistal tip is well past the lower ⅓^(rd) 1354 portion of the SVC 1352,referred to by the algorithm as zone 3. Note that FIG. 12 illustratesthat additional zones can be defined and reported by the process 1224according to its analysis of the detected P-wave characteristics.Indeed, FIG. 12 shows that a variety of zones can be defined, such as arange extending from −2 to +4, which are equally spaced at varyingdistances from the lower ⅓^(rd) portion 1354 of the SVC 1352. Of course,other zones and spacings can also be defined as part of the method 1200.

The zone assigned by the process 1224 is reported to a systemapplication 1218 of the system 10 at stage 1270. In one embodiment, thesystem application 1218 includes a controlling firmware or softwareapplication as executed by the processor 22 (FIG. 1) or other suitablecomponent of the system 10. Note that in one embodiment the sameprocessor, such as the processor 22 of the system console 20 (FIG. 1),can be employed to execute both the method 1200 and the systemapplication 1218. The above-described three zones, indicating proximityof the catheter distal end to the patient heart 1350 (FIG. 12) can bereported in stage 1270 to the system application 1218. Additional zonescan also be defined and reported, in another embodiment. The systemapplication 1218 can then use the reporting of such zones to conveypertinent information to the user of the system 10 to assist the user inplacing the catheter at a desired location within the vasculature, asdescribed further below.

The above-described method 1200 is iteratively executed in the presentembodiment so as to evaluate successive ECG complexes of the patient asdetected by the system 10. In other embodiments, non-iterative operationis possible. Once a sufficient number of zone reports (i.e., reports ofthe zone in which the stylet distal tip is located with respect to thepatient heart) according to the analysis of the P-wave by the method1200 are received by the system application 1218 of the system 10 (viastages 1270 and/or 1248), the display 30 (FIGS. 1, 2) can be updated toindicate the reported zone, if any, and assist the clinician indetermining when the distal tip of the catheter or other suitablemedical device has reached the desired intravascular location.

In light of the above, FIGS. 10A-10C show various examples of thedepiction of the zone reports provided by the method 1200 of FIG. 6 tothe system application 1218, on the display 30 of the system 10 (FIGS.1, 2). In particular, FIGS. 10A-10C show various depictions, orscreenshots 1320 of the display 30 during use of the system 10 to guideand place a catheter within the vasculature of a patient. As shown inFIG. 10A, an external ECG trace 1322 is present, as detected by theexternal ECG signal sensor component, which in the present embodimentincludes the external electrodes 136, as described further above. Anintravascular ECG trace 1324 is also depicted, as detected by theintravascular ECG signal sensor component, which in the presentembodiment includes the stylet ECG sensor assembly of the stylet 130.

A sensor image 1326 is also shown, which represents the sensor 50 (FIGS.1, 2) and its detection of the stylet distal tip. A stylet position icon1328 is shown superimposed on the sensor image 1326 to indicate positionof the stylet distal tip via magnet tracking in TLS mode, ECG trackingin the ECG mode just described, or a combination of both. Note that theicon 1328 in FIG. 10A includes a bullseye configuration, indicating thatthe system while in ECG tracking mode has not yet detected the styletdistal tip as having arrived at zone 1 proximate the lower ⅓^(rd)portion 1354 of the SVC 1352 (FIG. 12).

FIG. 10B shows the screenshot 1320 with the sensor image 1326 increasedin size, which is an option selectable by the clinician or automaticallyperformed by the system 10, in one embodiment. Note that the styletposition icon 1328 has changed to a diamond, which can be colored green,indicating that the system 10 has determined that the stylet distal tipis located within either zone 1 or 2 (FIG. 12), as reported to thesystem by the process 1224 (FIG. 6).

In FIG. 10C and according to one embodiment, the P-wave portions of theECG complexes shown in the external and internal ECG traces 1322, 1324of the screenshot 1320 are highlighted, such as by color, for clinicianconvenience. FIG. 10C shows that if the stylet distal tip is advancedbeyond the lower ⅓^(rd) portion 1354 of the SVC 1352 the process 1224 ofthe method 1200 would report a zone 3. This, in turn, causes the styletposition icon 1328 to change from a green diamond to a red octagon,indicating that further advancement of the stylet 130 and catheter 72should stop. Of course, other colors, shapes, designs, andconfigurations for the stylet position icon can be employed by thesystem 10. Indeed, further examples of position icons that can beemployed are found in U.S. Patent Application Publication No.2014/0188133, filed Mar. 7, 2014, and entitled “Iconic Representationsfor Guidance of an Indwelling Medical Device,” which is incorporatedherein by reference in its entirety.

FIG. 9 shows a zone reporting decision tree 1280 that is employed in thepresent embodiment by the system application 1218 to determine whenchanging/updating of the display 30 is warranted so as to accuratelyreflect the position of the stylet distal tip, and hence the catheterdistal tip. During execution of the method 1200 (FIG. 6) while thestylet 130 and catheter 72 are advanced within the patient vasculature,the display 30 will depict the stylet position icon 1328 as ayellow-colored bullseye, such as that seen in FIG. 10 on the sensorimage 1326, when no zone has been reported to the system application1218 by the process 1224. This situation corresponds to block 1282,marked “Y1” to indicate the yellow icon color. Note that in the presentembodiment the method 1200 will iteratively report a zone (stage 1270 inFIG. 6) or a no zone (stage 1248) to the system application 1218 duringexecution of the method and operation of the system 10.

When the process 1224 reports a zone 1 or 2 to the system application1218 (FIG. 6), advancement from Y1 block 1282 to block 1284, which ismarked “G1” to indicate an initial green state, occurs. When the process1224 iteratively reports a second successive zone 1 or 2, advancement ismade from G1 block 1284 to block 1286, which is marked “G2” to indicatea green state. This corresponds to the stylet position icon 1328 beingchanged from the yellow bullseye icon of FIG. 10A to a green diamondicon as seen in FIG. 10B.

Should the process 1224 then report a zone 3 or greater to the systemapplication 1218, advancement from the G2 block 1286 to block 1288,which is marked “r1” to indicate an initial red state, occurs. If theprocess 1224 iteratively reports a second successive zone 3 or greater,advancement is made from R1 block 1288 to block 1290, which is marked“R2” to indicate a red state. This corresponds to the stylet positionicon 1328 being changed from the green diamond of FIG. 10B to the redoctagon as seen in FIG. 10C.

Should the process 1224 then report a zone 1 or 2 to the systemapplication 1218, advancement from the R2 block 1290 back to the G1block 1284 is made to proceed as described above. This—as well assimilar advancement to the G1 block 1284 from the R1 block 1288 or theY1 block 1282—is indicated by the arrows 1294. Correspondingly,advancement to the R1 block 1288 from blocks 1282, 1284, or 1286 isindicated by the arrows 1296.

On any of the blocks 1282, 1284, 1286, 1288, and 1290, the lack of anyreporting from the process 1224 for a period of less than three secondscauses the system application 1218 to remain on the same designatedblock. This is indicated by the looped arrows 1292 adjacent each of theblocks 1282, 1284, 1286, 1288, and 1290.

On any of the blocks 1282, 1284, 1286, 1288, and 1290, the lack of anyreporting from the process 1224 for a period equal to or more than threeseconds causes the system application 1218 to revert to the Y1 block1282, with the corresponding change of the stylet position icon 1328.This is indicated by the dashed arrows 1302 leading to the Y1 block 1282from the blocks 1284, 1286, 1288, and 1290.

On the G2 block 1286 and the R2 block 1290, continued reporting from theprocess 1224 of the same zone causes the system application 1218 toremain on the same designated block. This is indicated by the loopedarrows 1298 and 1300 for the G2 block 1286 and the R2 block 1290,respectively.

FIG. 13 shows a zone reporting decision tree 1400 that is employed inone embodiment by the system application 1218 to determine whenchanging/updating of the display 30 is warranted so as to accuratelyreflect the position of the stylet distal tip, and hence the catheterdistal tip, during catheter insertion and positioning. In particular,the method 1400 is executed in one embodiment by the system application1218 in deciding how and when to update the depiction on the display 30,including the stylet position icon 1328 (see FIGS. 10A-10C), based onthe zone reports 1248, 1270 of the P-wave output 1216A of the process1224.

Method 1400 begins at stage 1402 by querying the zone report data (alsoreferred to as a “data set”) provided to the system application 1218 bythe process 1224 via P-wave output 1216A. Each zone report in the zonereport data includes either a no-zone indication or one of three zoneindications: low, high, and ideal, as described further below. In stage1404 it is determined whether the query count, or number of zone reportsprovided to the system application 1218, is equal to or greater than 50.If not, stage 1406 is executed, which adds another query, or zonereport, at stage 1402.

If the query count at stage 1404 yields 50 or more in quantity, stage1408 is executed, wherein the latest zone report is examined todetermine whether it reports a zone (corresponding to a “zone reported”at stage 1270 in FIG. 6) or if it reports a “no-zone” (corresponding toa “no zone reported” at stage 1248 in FIG. 6). If the latest zone reportis a no-zone, stage 1410 is executed, wherein a no-zone counter isincreased by one and the number of consecutive no-zones is counted.Then, at stage 1412, it is determined whether the number of countedconsecutive no-zones is equal to or greater than 20. If not, then stage1406 is executed, which adds another query, or zone report, to stage1402. If the answer at stage 1412 is “yes,” a zone counter is reset tozero at stage 1414, a high state is declared at stage 1432, in which thesystem application 1218 will depict an appropriate indication on thedisplay 30 (FIG. 2), for instance, indicating to the user that thecatheter can be advanced further and has not yet arrived at the desireddestination, in this case, the lower ⅓^(rd) portion 1354 of the SVC1352. In one embodiment, the depiction on the display 30 includes theyellow bullseye design of the stylet position icon 1328 as seen in FIG.10A. Once the depiction is displayed, the method 1400 reverts to stage1406 then stage 1402, wherein zone report data are queried anew. In oneembodiment, previously stored query data are disposed and new data areacquired. The above-described process is iterative with respect to theno-zone reporting.

Note that in the present embodiment, the query count of 50 in stage 1404corresponds to approximately five seconds of data as captured by thesystem 10 and the method 1200 (FIG. 6), that is, 500 hertz date ratereceived by the TLS sensor 50 processed in blocks of 50, yielding 10zone determinations per second. The buffer used to store the data ofstage 1402 operates on a first-in, first-out (“FIFO”) basis, ejectingthe oldest value in the buffer as a new value is received.

If, at stage 1408 the latest zone report reports a zone, stage 1416 isexecuted, wherein the no-zone counter is reset to zero and controladvances to stage 1418. At stage 1418, the data is analyzed, beginningwith the most recent zone reports, and at stake stage 1420, it isdetermined whether at least five zone reports are present in the queriedzone report data from stage 1402 (the at least five zone reports neednot be consecutive in the data). If not, the method reverts to stage1406, wherein another query is added to stage 1402 and the methodproceeds from there.

If the answer at stage 1420 is “yes,” stage 1422 is executed, whereinthe at least five zone reports are analyzed and at stage 1424, it isdetermined whether four or more of the zone reports are “low” zonereports, indicating that the distal tip of the stylet 130 has passed thelower ⅓^(rd) portion 1354 of the SVC 1352 (as in zones +3, +4 of FIG.12). If yes, a low state is declared at stage 1426, in which the systemapplication 1218 will depict an appropriate indication on the display 30(FIG. 2), for instance, indicating to the user that the catheter hasbeen advanced too far. In one embodiment, the depiction on the display30 includes the red octagon design of the stylet position icon 1328 asseen in FIG. 10C. Once the depiction is displayed, the method 1400reverts to stage 1406 then stage 1402, wherein zone report data arequeried anew. In one embodiment, previously stored query data aredisposed and new data are acquired.

If the answer at stage 1424 is “no,” stage 1428 is executed, wherein theat least five zone reports are analyzed and at stage 1430, it isdetermined whether three or more of the zone reports are “high” zonereports, indicating that the distal tip of the stylet 130 has not yetarrived proximate the lower ⅓^(rd) portion 1354 of the SVC 1352 (as inzones −2, −1, or 0 of FIG. 12). If yes, a high state is declared atstage 1432, in which the system application 1218 will depict anappropriate indication on the display 30 (FIG. 2), for instance,indicating to the user that the catheter can be advanced further. In oneembodiment, the depiction on the display 30 includes the yellow bullseyedesign of the stylet position icon 1328 as seen in FIG. 10A. Once thedepiction is displayed, the method 1400 reverts to stage 1406 then stage1402, wherein zone report data are queried anew. In one embodiment,previously stored query data are disposed and new data are acquired.

If the answer at stage 1430 is “no,” stage 1434 is executed, wherein theat least five zone reports are analyzed and at stage 1436, it isdetermined whether four or more of the zone reports are “ideal” zonereports, indicating that the distal tip of the stylet 130 has arrivedproximate the lower ⅓^(rd) portion 1354 of the SVC 1352 (as in zones +1or +2 of FIG. 12). If yes, an ideal state is declared at stage 1438, inwhich the system application 1218 will depict an appropriate indicationon the display 30 (FIG. 2), for instance, indicating to the user thatthe catheter has arrived at its intended destination according to thepresent embodiment. In one embodiment, the depiction on the display 30includes the green diamond design of the stylet position icon 1328 asseen in FIG. 10B. Once the depiction is displayed, the method 1400reverts to stage 1406 then stage 1402, wherein zone report data arequeried anew. In one embodiment, previously stored query data aredisposed and new data are acquired.

If the answer at stage 1436 is “no,” stage 1440 is executed, wherein theat least five current zone reports are analyzed and a decision made atone or more of three stages 1440, 1442, and 1444. At stage 1440, if theprevious zone determination on an immediately prior iteration of themethod 1400 yielded an ideal state and three of the five current zonereports are low zone reports, then a low state is declared at stage1426, which stage is executed as already described further above.

If the answer at stage 1440 is “no,” stage 1442 is executed, wherein ifthe previous zone determination on the immediately prior iteration ofthe method 1400 yielded an ideal state and two or more of the fivecurrent zone reports are ideal zone reports, then an ideal state isdeclared at stage 1438, which stage is executed as already describedfurther above.

If the answer at stage 1442 is “no,” stage 1444 is executed, wherein ifthe previous zone determination on the immediately prior iteration ofthe method 1400 yielded a low state and two or more of the five currentzone reports are low zone reports, then a low state is declared at stage1426, which stage is executed as already described further above.

If the answer at stage 1444 is “no,” a high state is declared at stage1432, which stage is executed as described further above. Once thedepiction is displayed pursuant stages 1426, 1432, or 1438, the method1400 reverts to stage 1406 then stage 1402, wherein zone report data arequeried anew. In one embodiment, previously stored query data aredisposed and new data are acquired.

Note that the method 1400 is iteratively run during the medical deviceplacement process using the system 10. Note also that the particularthreshold numbers used in evaluating the zone reports can vary from whatis described herein as may be appreciated by one skilled in the art.Also, more than three zone reports can be employed, in one embodiment.

Note that other modes for updating the display 30 according to zoneinformation reported by the method 1200 can also be employed, includingdifferent icons or symbols or output modes, differently colored icons,etc. More generally, other reporting decision trees can be utilized togovern depiction of zone information from the method 1200 on the display30 or other output mode by the system application 1218. In yet anotherembodiment, parameters other than zones can be reported by the method1200.

Note that the stages 1260-1264 of the process 1224 can be performedsimultaneously or in an order different than that shown in FIG. 6. Also,other parameters can be evaluated by the algorithm of the method 1200,including patient heart rate, isoelectric/baseline wander, and theuprightness of the detected QRS complex. For example, a patient heartrate threshold of between about 50 and about 150 beats per minute can beused as a parameter for evaluation by the method 1200 to ensure properintravascular placement of the medical device. In another example, anallowable baseline wander of +/−about 300 microvolts at 2.5 Hertz can beused as a parameter. In yet another example, a QRS complex lengthbetween about 0.08 and about 0.10 seconds in duration can be used as aparameter. These and other suitable parameters can be employed.Generally, it is noted that more or fewer stages can be included in themethod 1200 in other embodiments to assist in tracking and positioningthe catheter or other suitable medical device.

FIG. 11 shows the method 1200 according to another embodiment, whereininstead of both external and intravascular ECG sensor components used todetermine P-wave maximum, only the intravascular ECG sensor component isemployed. As such, no external electrodes, such as the externalelectrodes 136 (FIG. 2), are disposed on the skin of the patient.Instead, stages 1230, 1232, 1234, 1236, and 1240 are executed by using abaseline ECG signal. The baseline ECG signal is acquired using ECGsignals detected by the stylet sensor assembly of the stylet 130 (i.e.,the intravascular ECG sensor component). In particular, the baseline ECGsignal is acquired from the stylet ECG sensor assembly of the stylet 130when the stylet distal tip is disposed in the vasculature between theinsertion site 73 (FIG. 2) and about the shoulder region of the arm intowhich the stylet and catheter 72 are inserted (i.e., the right arm inthe example shown in FIG. 2). Note that, in another embodiment, theinsertion site can be on another limb of the patient, such as the leg,in which case the baseline ECG signal is acquired from the stylet ECGsensor assembly when the stylet distal tip is disposed between theinsertion site and the junction point of the limb (leg) with the torsoof the patient.

Detection of ECG signals when the stylet sensor assembly is positionedas described immediately above (with the insertion site disposed on thearm of the patient) approximates the detection of ECG signals from apair of external skin-placed electrodes in a “Lead II” configurationbased on Einthoven's triangle. As such, the ECG signal so detected willremain substantially static and can be used as a baseline reference ECGsignal against the intravascular ECG signal detected by the styletsensor assembly when the stylet 130 is advanced past the generalshoulder region of the arm into which the stylet and catheter areinserted. Such advancement will enable the stylet sensor assembly todetect the changing P-wave as the stylet nears the SA node of thepatient heart 1350 (FIG. 12). Thus, in the present embodiment the stages1230, 1232, 1234, 1236, and 1240 are executed similar to that describedfurther above in connection with the description of FIG. 6 while usingthe baseline ECG signal (part of the intravascular ECG signal data 1212)detected by the stylet sensor assembly upon initial insertion of thecatheter 72 and included stylet 130 into the vasculature but beforeadvancement past the shoulder region of the arm into which the catheterand stylet are inserted.

Note that the use and analysis of a baseline and intravascular ECGsignal that both originate from detection by an intravascular ECG sensorcomponent (i.e., the stylet sensor assembly of the stylet 130) asdescribed in connection with FIG. 11 enables in one embodiment theability for a clinician to observe conditions that may be evident onlyin the intravascular ECG signal and not evident in an external ECGsignal detected via an external ECG sensor component, such as theexternal electrodes 136 of FIG. 2. One example of such a conditionincludes intra-atrial blocks, for instance.

Embodiments disclosed herein may include a special purpose orgeneral-purpose computer including computer hardware, as discussed ingreater detail below. Embodiments within the scope of the presentdisclosure also include computer-readable media for carrying or havingcomputer-executable instructions or data structures stored thereon. Suchcomputer-readable media can be any available media that can be accessedby a general purpose or special purpose computer. By way of example, andnot limitation, computer-readable media can comprise physical (orrecordable-type) computer-readable storage media, such as, RAM, ROM,EEPROM, CD-ROM or other optical disk storage, solid-state storage,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to store desired program code means in the formof computer-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer.

In this description and in the following claims, a “network” is definedas one or more data links that enable the transport of electronic databetween computer systems and/or modules. When information is transferredor provided over a network or another communications connection (eitherhardwired, wireless, or a combination of hardwired or wireless) to acomputer, the computer properly views the connection as acomputer-readable medium. Thus, by way of example, and not limitation,computer-readable media can also comprise a network or data links whichcan be used to carry or store desired program code means in the form ofcomputer-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer.

Computer-executable instructions include, for example, instructions anddata which cause a general purpose computer, special purpose computer,or special purpose processing device to perform a certain function orgroup of functions. The computer executable instructions may be, forexample, binaries, intermediate format instructions such as assemblylanguage, or even source code. Although the subject matter has beendescribed in language specific to structural features and/ormethodological acts, it is to be understood that the subject matterdefined in the appended claims is not necessarily limited to thedescribed features or acts described above. Rather, the describedfeatures and acts are disclosed as example forms of implementing theclaims.

Those skilled in the art will appreciate that the embodiments herein maybe practiced in network computing environments with many types ofcomputer system configurations, including personal computers, desktopcomputers, laptop computers, message processors, hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network PCs, minicomputers, mainframe computers, mobiletelephones, PDAs, pagers, and the like. The embodiments may also bepracticed in distributed system environments where local and remotecomputer systems, which are linked (either by hardwired data links,wireless data links, or by a combination of hardwired and wireless datalinks) through a network, both perform tasks. In a distributed systemenvironment, program modules may be located in both local and remotememory storage devices.

Embodiments of the invention may be embodied in other specific formswithout departing from the spirit of the present disclosure. Thedescribed embodiments are to be considered in all respects only asillustrative, not restrictive. The scope of the embodiments is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A method for guiding a medical device to adesired location within a vasculature of a patient, the methodcomprising: detecting an intravascular ECG signal of the patient;identifying a P-wave of a waveform of the intravascular ECG signal, theP-wave varying according to proximity of the medical device to thedesired location; determining whether the identified P-wave is elevated;determining a deflection value of the identified P-wave when theidentified P-wave is elevated; and reporting information relating to alocation of the medical device within the vasculature of the patient atleast partially according to the determined deflection value of theelevated P-wave.
 2. The method for guiding as defined in claim 1,further comprising: detecting an external ECG signal of the patient;identifying an external P-wave of a waveform of the external ECG signal;and using the identified external P-wave in identifying the P-wave ofthe intravascular ECG signal.
 3. The method for guiding as defined inclaim 2, wherein identifying the external P-wave further includes:identifying a QRS complex of the waveform of the external ECG signal;identifying a T-wave of the waveform of the external ECG signal; anddetermining a RR interval between successive waveforms of the externalECG signal.
 4. The method for guiding as defined in claim 3, wherein theexternal ECG signal is detected by a pair of external electrodes placedon a skin of the patient.
 5. The method for guiding as defined in claim1, wherein the intravascular ECG signal is detected by a sensorcomponent included with a stylet removably received within the medicaldevice.
 6. The method for guiding as defined in claim 1, whereinidentifying a P-wave, determining whether the identified P-wave iselevated, and determining the deflection value are executed by aprocessor of a system operably connected with the medical device.
 7. Themethod for guiding as defined in claim 6, wherein identifying a P-wave,determining whether the identified P-wave is elevated, and determiningthe deflection value are executed iteratively by the processor.
 8. Themethod for guiding as defined in claim 1, wherein the medical deviceincludes a catheter and wherein the desired location is proximate alower portion of a superior vena cava of a heart of the patient.
 9. Themethod for guiding as defined in claim 1, wherein reporting informationrelating to the location of the medical device includes reporting one ofa plurality of zones, each zone relating to a proximity of the medicaldevice to a signal-emitting node of a heart of the patient.
 10. Themethod for guiding as defined in claim 1, wherein reporting informationrelating to a location of the medical device includes outputting theinformation to at least one of an audio device and a display device. 11.The method for guiding as defined in claim 1, wherein reportinginformation relating to a location of the medical device includesoutputting graphical information to a display device of a placementsystem for the medical device.
 12. The method for guiding as defined inclaim 11, wherein the graphical information includes a plurality oficons that correspond to a proximity of the medical device to asignal-emitting node of a heart of the patient.
 13. A method for guidinga medical device to a desired location within a vasculature of apatient, the method comprising: detecting an intravascular ECG signal ofa signal-emitting portion of a heart of the patient by an intravascularECG sensor component included with the medical device; and determiningwhether a P-wave of a waveform of the intravascular ECG signal iselevated based on a plurality of predetermined thresholds, the P-wavevarying according to a distance of the intravascular ECG sensorcomponent from the signal-emitting portion of the heart, thepredetermined thresholds relating to at least one of the following: (a)an amplitude of the P-wave of the intravascular ECG signal within apredetermined range; (b) a slope of the P-wave of the intravascular ECGsignal within a predetermined range; and (c) a noise component of theintravascular ECG signal within a predetermined range.
 14. The methodfor guiding as defined in claim 13, further comprising: determining adeflection value of the P-wave when the P-wave is elevated; andreporting information relating to a location of the medical devicewithin the vasculature of the patient at least partially according tothe determined deflection value of the P-wave.
 15. The method forguiding as defined in claim 13, wherein detecting the intravascular ECGsignal, determining whether the P-wave is elevated, and determining thedeflection value are performed iteratively.
 16. A system for guiding amedical device to a desired location within a vasculature of a patient,comprising: at least an intravascular ECG sensor for detecting anintravascular ECG signal of the patient; a processor that receives theintravascular ECG signal, the processor: identifying a P-wave of awaveform of the intravascular ECG signal, the P-wave varying accordingto proximity of the medical device to the desired location; determiningwhether the identified P-wave is elevated; determining a deflectionvalue of the identified P-wave when the identified P-wave is elevated;and reporting information relating to a location of the medical devicewithin the vasculature of the patient at least partially according tothe determined deflection value of the elevated P-wave; and an outputdevice that reports the information relating to the location of themedical device.
 17. The system for guiding as defined in claim 16,wherein the processor determining whether the identified P-wave iselevated further includes at least one of: determining whether at leastone of a frequency and an amplitude of the identified falls within apredetermined range; and determining whether a noise component of theintravascular ECG signal falls within a predetermined range.
 18. Thesystem for guiding as defined in claim 16, wherein the output deviceincludes a display of the system.
 19. The system for guiding as definedin claim 18, wherein the processor executes a decision tree, thedecision tree determining when to report the information relating to thelocation of the medical device.
 20. The system as defined in claim 19,wherein the medical device placement system further includes at leastone of a magnet tracking modality and an ultrasound imaging modality.21. In a guidance system including a medical device for insertion into avasculature of a patient, an external ECG sensor component, and anintravascular ECG sensor component included with the medical device, amethod for guiding the medical device, the method comprising: (a)identifying a P-wave from a waveform of an intravascular ECG signal fromthe intravascular ECG sensor component after insertion of the medicaldevice into the vasculature; (b) determining whether at least one of afrequency and an amplitude of the identified P-wave falls within apredetermined range; (c) determining whether a noise component of theintravascular ECG signal falls within a predetermined range; and (d)determining whether the identified P-wave is at an elevated state basedupon the determinations of stages (b) and (c).
 22. The method forguiding as defined in claim 21, further comprising: (e) determining adeflection value for the identified P-wave when the identified P-wave isat an elevated state as determined in stage (d).
 23. The method forguiding as defined in claim 22, further comprising: (f) depicting aposition of the medical device based on the deflection value asdetermined in stage (e).
 24. The method for guiding as defined in claim23, wherein a processor of the system executes a decision tree, thedecision tree determining an aspect of depicting the position of themedical device.
 25. The method for guiding as defined in claim 24,wherein the decision tree iteratively queries a data set of a pluralityof zone reports until at least 50 zone reports are acquired.
 26. Themethod for guiding as defined in claim 24, wherein the processor depictsthe position of the medical device when at three of five zone reportsfrom the data set are identical.
 27. The method for guiding as definedin claim 21, further comprising: identifying an external P-wave of awaveform of an external ECG signal from the external ECG sensorcomponent; and using the identified external P-wave to identify theP-wave of the intravascular ECG signal in stage (a).
 28. A method forguiding a catheter to a desired location within a vasculature of apatient, the method comprising: inserting a distal portion of thecatheter into the vasculature via an insertion site on a limb of thepatient; detecting a baseline ECG signal of the patient via an ECGsensor included with the catheter, the baseline ECG signal beingdetected when the distal portion of the catheter is disposed between theinsertion site and a junction point of the limb with the torso of thepatient; attempting to identify a baseline P-wave of a waveform of thebaseline ECG signal; identifying an intravascular P-wave of a waveformof an intravascular ECG signal, the intravascular ECG signal beingdetected when the distal portion of the catheter is disposed at alocation distal to the junction point of the limb, the intravascularP-wave varying according to proximity of the catheter to the desiredlocation; determining whether the identified intravascular P-wave iselevated; determining a deflection value of the identified intravascularP-wave when the identified intravascular P-wave is elevated; andreporting information relating to a location of the catheter within thevasculature of the patient at least partially according to thedetermined deflection value of the elevated identified intravascularP-wave.
 29. The method for guiding as defined in claim 28, whereinidentifying the intravascular P-wave is at least partially is executedusing information relating to the identification of the baseline P-wave.